Projection zoom lens
AssigneeSeiko Epson Corporation
InventorNobutaka Minefuji
Life of this patent
Estimating the term…
Abstract
A projection zoom lens is formed of the following lens groups sequentially arranged from the high magnification side: a first lens group fixed at the time of zooming and having negative power; a second lens group moved along the optical axis at the time of zooming and having negative power; a third lens group moved at the time of zooming and having positive power; a fourth lens group moved at the time of zooming; and a fifth lens group fixed at the time of zooming and having positive power. When the total lens system operating at the wide angle end has a focal length Fw, and the first lens group has a focal length F1, the following conditional expression is satisfied. −0.5<Fw/F1<−0.1 (1)
Claims12
A projection zoom lens comprising at least the following five lens groups sequentially arranged from an enlargement side:
- a first lens group fixed at the time of zooming and having negative power;
- a second lens group moved at the time of zooming and having negative power;
- a third lens group moved at the time of zooming and having positive power;
- at least one lens group moved at the time of zooming;
- and
- a last lens group fixed at the time of zooming and having positive power,
- wherein the first lens group is formed of a single negative lens having a steep concave surface facing a reduction side, and
- wherein when the total lens system operating at a wide angle end has a focal length Fw, and the first lens group G1 has a focal length F1, the following conditional expression (1) is satisfied:
- −0.5<Fw/F1<−0.1 (1).
Dependencies are inferred from the claim text.